This invention relates to a photosensitive member with a photosensitive layer comprising a new distyryl compound.
In general electrophotography, many methods for forming copied images are known. For example, the surface of a photosensitive member is charged and irradiated to form electrostatic latent images thereon, the electrostatic latent images are developed to visible images by a developer, and then the developed images are fixed directly onto the photosensitive member (this method is referred to as a direct method). Alternatively, developed electrostatic latent images on a photosensitive member which are made visible by a developer are transferred to a copying paper and then, the transferred images are fixed on the copying paper (this method is referred to as a powder transferring method). In another method, electrostatic latent images on a photosensitive member are transferred onto a copying paper, the transferred electrostatic latent images are developed by a developer and then fixed on the copying paper (referred to as an electrostatic latent image transferring method).
With respect to photosensitive materials conventionally used for forming a photosensitive layer, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide and the like are known.
These photoconductive materials have many advantages, such as ability to be charged to an adequate potential, low loss of electrical charges in the dark, a rapid dissipation of electrical charges with irradiation of light and the like. However, they have disadvantages. For example, a photosensitive member based on selenium is difficult to produce, has high production costs and difficult to handle due to inadequate resistivity to heat or mechanical impact. A photosensitive member based on cadmium sulfide or zinc oxide has defects such as its unstable sensitivity in a highly humid environmental and loss of stability with time because of the deterioration of dyestuffs, added as a sensitizer, by corona charge and fading with exposure.
Many kinds of organic photoconductive materials such as polyvinylcarbazole and so on have been proposed. These organic photoconductive materials have superior film forming properties, are light in weight, etc., but inferior in sensitivity, durability and environmental stability compared to the aforementioned inorganic photoconductive materials.
A photoconductive organic compound of low molecular weight is preferable in that electrophotographic properties or physical properties of a layer can be controlled by selecting the kind of binder resin, composition ratio or the like, but the high compatibility of the photoconductive organic compound with the binder resin is required because the photoconductive organic compound is used in combination with the binder resin.
A photosensitive member with an photoconductive organic compound of high molecular weight or low molecular weight dispersed in a binder resin has defects, such as high residual potential caused by many traps of carriers, low sensitivity or the like. In order to overcome those defects, it has been proposed that the photoconductive compound is used together with a charge transporting material.
Further, a function-divided photosensitive member has been proposed, in which charge generating function and charge transporting function are showed by separate materials. In such a function-divided photosensitive member, many kinds of organic compounds are proposed as a charge transporting material incorporated in a charge transporting layer. But, they have various problems in actual act. For example, U.S. Pat. No. 3,189,447 proposes use of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, but this compound has only a poor compatibility with binders and is liable to separate out as crystals. Further U.S. Pat. No. 3,820,989 discloses use of diarylalkane derivatives having a high compatibility with binders. However, the photosensitive member containing the derivatives undergoes variations in sensitivity when repeatedly used. Japanese Patent Laid-Open No. 54-59143 discloses a hydrazone compound, which show relatively good residual potential properties. However, the hydrazone compound is inferior in chargeability, repetition properties or the like.
As above mentioned, the fact is that there are almost no preferable organic compound of low molecular weight suitable for practical use.
Japanese Patent Laid-Open Nos. 60-175052 and 62-120346 disclose a distyryl compound excellent in chargetransportability, but the distyryl compound is completely different from the compound of the present invention disclosed below.